Errors in CAPI display callbacks and focus-related callbacks tend to be invoked repeatedly. Therefore display of panes where such an error occurs ("broken" panes) is now normally disabled until the Debugger tools exists. Therefore while debugging such errors some panes will not be displayed correctly.
Exiting the Debugger tool will allow the error to recur, so to prevent this in some cases there is now a restart to disable the display of the broken pane permanently.
LispWorks Release Notes and Installation Guide - 23 Dec 2011